Chronic Implantation of Whole-cortical Electrocorticographic Array in the Common Marmoset

Summary

We have developed a whole-cortical electrocorticographic array for the common marmoset that continuously covers almost the entire lateral surface of cortex, from the occipital pole to the temporal and frontal poles. This protocol describes a chronic implantation procedure of the array in the epidural space of the marmoset brain.

Abstract

Electrocorticography (ECoG) allows the monitoring of electrical field potentials from the cerebral cortex with high spatiotemporal resolution. Recent development of thin, flexible ECoG electrodes has enabled conduction of stable recordings of large-scale cortical activity. We have developed a whole-cortical ECoG array for the common marmoset. The array continuously covers almost the entire lateral surface of cortical hemisphere, from the occipital pole to the temporal and frontal poles, and it captures whole-cortical neural activity in one shot. This protocol describes a chronic implantation procedure of the array in the epidural space of the marmoset brain. Marmosets have two advantages regarding ECoG recordings, one being the homologous organization of anatomical structures in humans and macaques, including frontal, parietal, and temporal complexes. The other advantage is that the marmoset brain is lissencephalic and contains a large number of complexes, which are more difficult to access in macaques with ECoG, that are exposed to the brain surface.These features allow direct access to most cortical areas beneath the surface of the brain. This system provides an opportunity to investigate global cortical information processing with high resolutions at a sub-millisecond order in time and millimeter order in space.

Introduction

Cognition requires the coordination of neural ensembles across widespread brain networks, particularly the neocortex that is well-developed in humans and believed to be involved in higher cognitive behaviors. However, how the neocortex achieves this cognitive behavior is an unsolved issue in the neuroscience field. Recent development of thin, flexible electrocorticographic (ECoG) electrodes enables conduction of stable recordings from large-scale cortical activity¹. Fujii and colleagues have developed a whole-cortical ECoG array for macaque monkeys^2,3. The array continuously covers almo....

Protocol

This protocol has been performed on 6 common marmosets (4 males, 2 females; body weight = 320-470 g; age = 14-53 months). All procedures were carried out in accordance with the recommendations of the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals. The protocol was approved by the RIKEN Ethical Committee (No. H28-2-221(3)). All surgical procedures were performed under anesthesia, and all efforts were made to minimize the number of animals used as well as their discomfort.

1. Preparation

1. Obtain a structural magnetic resonance image (MRI) of each individual brain. This will be used to identify e....

Results

The whole-cortical ECoG array can simultaneously capture neuronal activity from the entirety of a hemisphere. Figure 4 shows examples of auditory evoked potentials (AEPs) from multiple auditory areas in an awake marmoset. ECoG recordings were conducted in passive listening conditions. Each marmoset was exposed to auditory stimuli, which consisted of randomized pure tones with 20 types of frequency. Then, we calculated AEPs by averaging ECoGs aligned with onse.......

Discussion

For successful implantation, animals should be provided with adequate nutrition before and after surgery. Short operating time is also important to optimize the animal's recovery. Preparations should be finished at least one day before surgery. To reduce operating time, previous craniotomy training with electrode array insertion in terminated animals for other experimental purposes is recommended. Table 1 shows an example of the time course for this protocol.

We modif.......

Materials

Name	Company	Catalog Number	Comments
Beaker (100 cc)			Outocrave
Cotton ball			Outocrave
Absorption triangles	Fine Science Tools Inc.	18105-03	Outocrave
Cotton swab with fine tip	Clean Cross Co., Ltd.	HUBY340 BB-013	Outocrave
Gauze			Outocrave
Towel forceps			Outocrave
Scalpel handle			Outocrave
Needle Holder			Outocrave
Iris Scissor			Outocrave
Micro-Mosquito Forceps			Outocrave
Adson, 1x2 teeth			Outocrave
Bone Curette			Outocrave
Micro spatura	Fine Science Tools Inc.	10091-12	Outocrave
Needle Holders, 12.5cm, Curved, Smooth Jaws	World Precision Instruments	14132	Outocrave
Vessel Dilator, 12cm, 0.1mm tip	Fine Science Tools Inc.	18131-12	Outocrave
Vessel Dilator, 12cm, 0.2 mm tip	Fine Science Tools Inc.	18132-12	Outocrave
Fine-tipped rongeur	Fine Science Tools Inc.	16221-14	Outocrave
Manipurator of a stereotaxic frame			Gas sterilization
Wrench for the manipurator			Gas sterilization
Hand-made fixture for the connector			Gas sterilization
Silicon cup for dental acril			Gas sterilization
Silicon cup hlder			Gas sterilization
Paintbrush			Gas sterilization
Pencil			Gas sterilization
Micro screw, 1.4 mm x 2.0 mm	Nippon Chemical Screw Co., Ltd.	PEEK/MPH-M1.4-L2	Gas sterilization
Screw driver for the micro screw			Gas sterilization
Micromotor handpiece of a drill			Gas sterilization
Stainless steel burr, 1.4 mm			Gas sterilization
Stainless steel burr, 1.0 mm			Gas sterilization
Drill bit, 1.2 mm			Gas sterilization
Rubber air blower			Gas sterilization